Pinch-hitter Chad Tracy slashed a two-run, seventh-inning single to center Tuesday night to break up a scoreless tie and lead the Washington Nationals to a 3-1 victory over the Padres at Petco Park.

Tracy’s sharp, one-out grounder through a drawn-in infield ended a pitching duel between left-handers Gio Gonzalez of the Nationals and Clayton Richard of the Padres.

“We said going into that game it was going to come down to one hit,” Padres manager Bud Black said. “That was the key, and they got it.”

Washington’s third straight win and 11th in the last 13 games ended the Padres’ season-best, two-game winning streak.

The six shutout innings by Gonzalez extended two other Nationals streaks. Washington starting pitchers have worked 22 straight scoreless innings and Gonzalez has his own personal streak of 20 straight scoreless innings.

The Padres, who had five hits to the Nationals’ four, did score against the Washington bullpen in the seventh and squandered an opportunity for more.

Cameron Maybin drew a walk from Craig Stammen leading off the seventh and Orlando Hudson followed with a single, extending his hitting streak to seven straight games.

Parrino stole second, putting Padres at second and third with one out, during a battle between Clippard and Padres pinch-hitter Mark Kotsay. Kotsay fouled off eight, two-strike pitches in the 12-pitch duel before popping out to short. The threat ended when Chris Denorfia grounded out to third.

Washington added an insurance run in the ninth after Wilson Ramos’ liner to right sailed past Will Venable’s glove for a three-base error. It was the fifth error of the season for Venable. Wilson scored on a two-out single by pinch-hitter Rick Ankiel.

The Nationals had only one hit in the first six innings against left-hander Clayton Richard, although the Padres starter had to pitch out of three jams to keep the game scoreless going into the top of the seventh.

“Clayton was solid. His velocity was up, his movement was outstanding, much better than we saw the last two times,” Black said. “He had a little better arm angle.”

Former Padre Xavier Nady opened the seventh with a double to left, marking the second time in three innings that Washington had a lead-off double against Richard, who had allowed no hits in the first four innings.

After catcher Wilson Ramos walked, Steve Lombardozzi, who is subbing at third for the injured Ryan Zimmerman, sacrificed the runners to second and third. Tracy followed with his sharply-hit single between Hudson and second base.

Black was ejected for the second time this season and for the 15th time in his managerial career for arguing a balk call by plate umpire Lance Barrett in the sixth.

With two out in the sixth, Mark DeRosa drew a walk and moved to second when Richard balked on a pick-off throw to first.

Clearly, the Padres did not agree with the balk call made by home plate umpire Barrett. Black immediately went to the mound and waited for Barrett to approach to break up the meeting. After engaging Barrett on the mound, Black followed Barrett back toward the plate and was ejected.